Plastic Coil on the W E I G H T of Day

U T E R I N E distention results in shortened estrous cycles in the ewe (Moore and Nalbandov, 1953; Nalbandov et al., 1955; Inskeep et al., 1962), in the bovine (Yamauchi and Nakahara, 1958; Hansel and Wagner, 1960; Yamauchi, 1963; Hawk et al., 1964) and in the guinea pig (Moore, 1961; Donovan and Traczyk, 1960; Bland and Donovan, 1965). The mechanisms involved in the precocious estrus demonstrated by these experiments are not known. In preliminary experiments in this laboratory it appeared that the insertion of a plastic coil into one uterine horn of the ewe resulted in shorter estrous cycles, when the coil was in a uterine horn adjacent to the ovary containing the corpus luteum (CL) than when the coil was in the opposite horn. In addition, in ewes with a CL in each ovary, the CL in the ovary adjacent to the horn containing the coil appeared to regress first. These preliminary experiments suggested that a plastic coil in one uterine horn of the ewe exerts a local "inhibitory" influence on the CL. The present experiment was designed to test the validity of these preliminary observations.